(1) Field of the Invention
The present invention pertains to a method of assembling articles using laser projection devices and a photoreactive material. More specifically, the present invention pertains to a method of assembling an article using one or more laser projectors and a material that is applied to the component parts of the article being assembled, where the material reacts when it is exposed to the laser light emitted by a projector. The material is applied to the article being assembled and when exposed to the laser light, the appearance of the material changes to mark a location on the material and thereby mark a location on the article where an assembly operation is to take place.
(2) Description of the Related Art
As a result of the competitive business environment, in businesses involving the assembly of large-scale articles such as automobiles, aircraft, large home appliances and others, there is a need to streamline the assembly of the component parts of the articles. A reduction in assembly time results in a reduction in manufacturing costs.
In the assembly of articles requiring a high degree of precision, specialized xe2x80x9chardxe2x80x9d tooling is used to locate critical features of the component parts, for example fastener holes and fasteners, and to accurately position component parts relative to each other. As a further example, in assembling sections of a sheet metal body to a frame of an article such as an automobile or aircraft, a tool is manually positioned in engagement with a portion of the frame and a portion of the sheet metal section to properly position the sheet metal section relative to the frame. This enables the sheet metal section to be accurately attached in its desired position relative to the frame. In the assembly of a large article such as an automobile or aircraft, a large number of assembly tools would be designed and manufactured, with each tool being used to accurately position different component parts of the article being assembled. Each of these assembly tools is expensive to design, to manufacture, and to store and maintain. The use of assembly tools also contributes to inefficiencies in assembling of an article because an individual involved in the assembly of the article must retrieve, use and then store the assembly tool each time it is utilized in the assembly of the article.
Laser projection systems were designed to overcome the disadvantages associated with the use of assembly tools in the assembling of large-scale articles requiring precision assembly. Laser projection systems project laser light onto the component parts of the article being assembled. Typically, the software of the laser projection system utilizes a computer aided design (CAD) model of the article being assembled and makes calculations based on the CAD model to direct the laser light beam of the laser projection system in the desired pattern. The projected laser light is used to accurately locate machined portions of the component parts. For example, the laser light projection would be used to accurately locate drilled holes. Laser projection systems are also used to accurately project illuminated lines and curves onto the surfaces of the article being assembled to precisely identify assembly locations of component parts relative to each other during the assembly of the parts. The projection of the lines and curves onto the article being assembled is useful for, among other things, locating where component parts are to be assembled on the article without requiring hard tooling, and for confirming the configurations of the article when compared to the nominal design dimensions of the article.
However, one of the drawbacks in using layer projection systems in the assembly of articles is that the line of projection of the laser light to the assembly area must be maintained. In the assembly of large articles such as automobiles and aircraft, it is often necessary for several individuals to work in the assembly area assembling component parts of the article. As the individuals move about in the assembly area, they often move into the path of the laser light projection, thus obstructing the projection and the display of assembly information on the article provided by the laser light. To overcome this problem, it was necessary to xe2x80x9cscribexe2x80x9d or trace the projected information onto the component part. This added significantly to the assembly time, and often lead to errors in the xe2x80x9cscribedxe2x80x9d information.
The present invention provides a method of assembling articles, for example automobiles, aircraft, and other types of articles that require precision positioning of at least some of their component parts, using light projection systems. The method of the invention makes use of known light projection systems, such as the model LPT1 manufactured by Laser Projection Technologies of Londonderry, N.H. The operation of the laser projection devices of the system of the invention is controlled by control software of the system, as is known in the art. A principle benefit of the invention is obtained by the use of a photoreactive material in conjunction with the laser projection system. The photoreactive material is applied to the surface of a component part of the article being assembled, and the laser light of the system produces a semi-permanent mark or indication on the surface of the component part through the reaction of the laser light with the photoreactive material. The markings produced by the photoreactive material on the component parts provide assistance to the individuals assembling the component parts in precisely positioning the component parts and/or checking the positioning of the component parts during assembly of the article. With the marks being produced on the component parts by the reaction of the laser light with the photoreactive material, the marks are not obstructed by the individuals assembling the article moving in front of the projected laser light. Because the individuals assembling the article are free to move about the assembly area without concerns for obstructing the projected laser light, the assembly of the article becomes more time efficient and more cost efficient.
The method of assembly of the present invention employs several of the known method steps of assembling an article employing projected laser light. At least one component part of the article to be assembled is positioned in an assembly area, and one or more laser light projectors are positioned in the assembly area. The laser light projector is controlled to emit laser light toward the component part in the assembly area where the laser light will be projected onto a surface of the component part.
A photoreactive material is applied to the surface of the component part in the area illuminated by the laser light. The photoreactive material can be provided in several forms. As one example, the material could be in the form of a self-adhesive tape or film applied to the surface of the component part. The photoreactive material can also be applied to the surface of the component part as a liquid that is sprayed onto the component part, as a dust that is dusted onto the component part, as a paste that is rubbed onto the component part, etc. When the laser light illuminates the photoreactive material applied to the surface of the component part, the pattern of the laser light projection creates a marking on the photoreactive material.
Movement of the laser light can be controlled to create a variety of different types of markings on the photoreactive material applied to the surface of the component part. The laser light can be moved to create cross-hair indications on the treated surface of the component part where holes are to be produced in the part, or where fasteners are to be located on the part. Lines can be formed on the treated surface of the component part by the movement of the laser light to provide a visual indication of the position of where a second component part is to be positioned relative to the one component part when assembling the two parts together. In addition, the movement of the laser light could project graphics onto the photoreactive material applied to the surface of the component part that provide information on a second component part to be assembled to the one component part, for example dimensions and materials of a fastener to be used with the one component part.
After the assembly of the article is completed, the photoreactive material applied to the surfaces of the component parts is removed. The removal of the photoreactive material is dependent on the form of the photoreactive material used. For example, the photoreactive material applied as a liquid spray would preferably be water based, enabling the easy removal of the photoreactive material from the surface of the assembled article by spraying or wiping water over the surface. A photoreactive material applied as a dust to the surface of the article component parts could be removed by a vacuum or by wiping the material from the surface. Photoreactive material applied to the surface of the component part as a paste would preferably be water based, enabling easy removal of the paste from the part""s surface by spraying or wiping water over the surface. The material applied as a tape could be pulled from the article after assembly.
The method of the invention provides the benefits of the use of laser projection systems in the assembly of articles, without the associated disadvantage of avoiding interruption of the projected laser light. The method enables the maintaining of the accuracy of the laser projected data, as well as providing a quick and efficient manner of delivering required assembly information directly to the individuals assembling the article.